[unreadable] The goal of this proposal is to develop dedicated, high resolution, computer tomography (CT) equipment for examination of excised specimens during surgical breast biopsies and surgical breast conserving therapies. The localization of lesion margins relative to the specimen margins, and estimating the orientation and extent of lesions that may extend beyond the specimen margins is of paramount importance during the surgical procedure. The radiological examination of the specimens needs to be performed very quickly within a few minutes in order to give surgeons the required feedback and to minimize the duration of the operation. [unreadable] [unreadable] The radiological examination of the excised specimens to aid during surgery is common practice in the US and worldwide. However, the equipment used in these procedures is not optimized for this task. Currently used equipment lacks the required contrast and does not have high enough spatial resolution for sufficient differentiation of tissues based on physical density and effective atomic number. For these reasons, we propose a new approach which combines development of a new, high resolution digital imaging detector based on Hgl2 polycrystalline x-ray converter coupled to a silicon CMOS readout circuit and use of a computer tomographic imaging technique for further enhancement of the image contrast. In Phase I of the project, our effort will be concentrated on the development of a prototype CMOS readout module that can be used as the substrate for depositing the Hgl2 films onto, and to show feasibility of the design and film deposition concepts. In Phase II we will optimize the design of the CMOS readout chip for full optimization for the application, increase the overall active area of the chip, and optimize the Hgl2 deposition as required. The final x-ray imager will be constructed in Phase II by tiling eight individual detector modules for a total area of about 100 mm by 100 mm. In Phase II, we will develop a gantry to support the x-ray detector, the micro focus x-ray tube and the specimen. We will provide a mechanism for the rotation of the specimen under computer control (detector and x-ray tube will be stationary). Also, we will develop software for reconstruction of the data in order to obtain the highest quality tomographic images. The prototype system will be tested with phantoms at Photon Imaging, Inc. and with real tissue samples at UCLA. [unreadable] [unreadable]